Showing posts with label disease. Show all posts

Pestilence - Deadlier than war

"Everybody knows that pestilences have a way of recurring in the world; yet somehow we find it hard to believe in ones that crash down on our heads from a blue sky" ‒ Albert Camus, The Plague, 1948

The only top predator left to infect

When humans start putting extreme pressure on local ecosystems, through for example overpopulation and deforestation, communities become more susceptible to emerging or novel zoonotic diseases as natural habitats disappear and exposure to pathogens increases. Several of today’s most pervasive diseases originally stemmed from domestication of livestock some 10,000 years ago. For example, tuberculosis, measles, and smallpox emerged following the domestication of wild cattle. Many pathogens that are currently passed from person to person, including influenza, Ebola and HIV, were formerly zoonotic but have mutated and adapted to human hosts. Today, wild animals are significantly more likely to be a source for animal-to-human spillover of viruses than domesticated species. According to one recent study, wild rodents are the most common source (58%) of spillover of zoonotic viruses, followed by primates and bats. Wildlife habitat destruction or encroachment, changes in surface waters, industrial monocultures, chemical pollution, uncontrolled urbanization, migration, international travel and trade have all increased the risk of disease spread in humans and the potential for a pandemic.

Toxic Cocktail

We know that our highly interconnected global society is very vulnerable to disruptions in food, water and energy supply. Another threat to the continuation of our civilization is global toxification. The 30 million tonnes a year global output in synthetic chemicals has left no living creature on Earth without these chemicals in its organs. The full impact of the chemical soup we are all living in whether we are a whale or a human are yet unknown. However, we know that the emergence of widespread antibiotic resistance is likely to cross paths with our exhausted immune systems compromised by chemical contamination, and the fact that with such high population density in many urban areas we are increasingly vulnerable to pandemics.

Exposure of fish and wildlife in urban regions due to continuous release of Endocrine Disrupting Chemicals in oceans and to the atmosphere.Source: WHO, 2012

Antibiotic Resistance

The fact that some antibiotics no longer work in people who need them to treat infections is now a major threat to public health, according to WHO. Over the last 30 years, no major new types of antibiotics have been developed.
According to a recent study published in the journal Lancet Infectious Diseases, scientists in China have discovered significantly increased levels of bacteria resistant to the antibiotic colistin in pigs. The drug is a last line of defense against a host of bacterial infections, many of which are common in people. Researchers have linked the growing prevalence of “super-germs” to the overuse of antibiotics in food animals. The drugs, used predominantly in the Chinese livestock industry, can keep animals healthy in an industrialized food process, but their use over time can embolden the very bacteria they were designed to fight against. In 2005, the European Union banned the use of antibiotics in livestock for non-medicinal purposes, but the drugs are still widely used across the continent, and are rampant in the agricultural industry in the United States. As people in wealthier regions run out of effective antibiotics, they come to share the lot of people in poorer regions who can’t afford them to begin with. In April 2014, the WHO declared that the problem “threatens the achievements of modern medicine. A post-antibiotic era — in which common infections and minor injuries can kill — is a very real possibility for the 21st century.”

Historical Pandemics


The Plague
The bacterium Yersinia pestis carried by fleas on rodents has caused at least three human plague pandemics, the Justinian Plague (6–8th centuries), the Black Death (14–17th centuries) and third Plague (19–20th centuries). In 541 A.D., the Justinian Plague caused 5,000 deaths per day in Constantinople, killing an estimated 25 million people globally. It spread from central Asia or Africa across the Mediterranean into Europe and may have contributed to the end of the Roman empire, marking the transition from the classical to the Medieval period. The Black Death arrived in the Eastern Mediterranean in 1347 and struck Italy, southern France with vehemence in 1348, came to England at the end of that year and spread northwards reaching Scandinavia in 1350. 

Larger cities were the worst off, as population densities and close living quarters made disease transmission easier. Cities were filthy with poor sanitation, infested with lice, fleas, and rats, and subject to diseases related to malnutrition and poor hygiene. Where the plague raged, it raged for a couple of months and then spent itself. The Black Death killed an estimated 100 million people over 7 years. Religious fanaticism in the wake of the Black Death lead to the persecution of groups such as Jews, friars, foreigners, beggars, lepers and Romani, as Europeans thought that they were to blame for the crisis. Subsequent outbreaks of this disease occurred in 8–12 year cycles for two centuries after the initial epidemic, with estimated mortality of 15–40%. The emergence of these plague pandemics might be tightly linked to climatic instability as all were preceded by periods of exceptional rainfall and ended during periods of climatic stability.
Hypothetical scenario for the geographic spread of Yersinia pestis. Source: Wagner et al. (2014)

The Spanish Flu
In 1918-19, the Spanish flu (H1N1) killed roughly 100 million people and infected 500 million people while affecting working age people (15–54 year olds) most severely. WWI was raging at the time and governments tried to control the public by limiting free speech. The pandemic was known as Spanish flu because Spain was not at war, had a more free press, and could report on the illness. Most of Europe had a censored press. In the U.S. the Sedition Act 1918 was passed, extending the Espionage Act of 1917 to cover a broader range of offenses, notably speech and the expression of opinion that cast the government or the war effort in a negative light. The 1918–1919 influenza pandemic swept across countries during a time when patriotism was more important than truth. Thus, intimidation and propaganda were part of the communication culture. People heard from authorities and newspapers that everything was going fine, but at the same time, bodies were piling up.
Emergency hospital during 1918 influenza pandemic, Camp Funston, Kansas.
Source: Otis Historical Archives Nat'l Museum of Health & Medicine (CC-BY 2.0)


War and disease

According to the WHO, previous to the conflict in Syria, more than 90% of Syrian children were vaccinated against disease like measles and polio. Since the fighting in Syria began almost 5 years ago, half of all health workers have left the country, medical supplies are scarce and most facilities are in decay. Some 20 million people have fled their homes in the MENA region. Countries like Jordan and Lebanon are under immense pressure as demand on services for health, water and sanitation have increased exponentially. The low immunization rates among those living in and fleeing from conflict zones, endangers the lives of people across the entire region. The recent outbreak of polio in Syria led to its resurgence in Iraq, which had been free of the disease for 14 years, and in 2013, Jordan experienced a new outbreak of measles. In Yemen there has been an upsurge in cases of measles and dengue fever due to lack of basic health care and collapsed water and sanitation facilities. WHO estimates show that 2.6 million children under 15 years of age in Yemen are at risk of measles; 2.5 million under 5 are at risk of diarrhoeal disease and another 1.3 at risk of acute respiratory infections.

Second order effects

Limiting the disruption of critical infrastructures during a pandemic is important for the survival and health of society (i.e., electricity, water, and food) as most medical and public health responses to a pandemic depend on these infrastructures. The food system’s dependence on the transportation system creates a major vulnerability. On average, food travels 2092 km (1,300 miles) from farm to fork. The global food system functions in a just-in-time economy where food inventories are intentionally kept at such low levels that food arrives just in time for consumption. Since inventories are kept very low, there is vulnerability to unanticipated variations in flow. Increasing stocks of food costs money and decreases profits, therefore, agricultural businesses are reluctant to build food security resilience via stockpiling. The Ebola epidemic that began in 2014 has caused severe food shortages in West Africa. As of November 2014, the World Food Program estimated that 460,000 additional individuals became food insecure in Liberia, Sierra Leone, and Guinea as a result of production and trade reductions. According to a recent study, a severe pandemic with <25% reduction in labor availability could create widespread food shortages in the US. This likely applies to other countries as well, especially those with insufficient resources and food production at home. 

Brace for impact: Super El Niño


As I have mentioned in a previous post, 2015/16 El Niño period have shown signs of becoming stronger than the devastating 1997/98 El Niño. Now weekly measurements are showing that it indeed has passed the record high of 1997/98 with temperatures in the central Pacific of 3°C above normal. November is likely to be strongest month of the El Niño season that lasts until spring next year.

The ongoing El Niño has already caused a number of serious impacts globally. For example, warmer waters have lead to major coral bleaching events and according to the UN, 11 million children are at risk from hunger, disease and lack of water in eastern and southern Africa, while 2.3 million people in Central America will need food aid as El Niño exacerbates a prolonged drought.

Regional Impacts


South East Asia: Dryer conditions in Southeast Asia has helped fuel massive peatland wildfires in Indonesia. This has caused dense haze to cover many parts of Indonesia and neighbouring countries with serious health impacts for local populations and has released a huge amount of greenhouse gasses to the atmosphere, making Indonesia a major contributor to climate change.


South Asia: Lack of precipitation in India due to changes in the southwest monsoon has also caused dryer conditions and risk of drought with potentially serious impacts on farmers and subsistence livelihoods. Especially since India suffered a deficient monsoon, lack of precipitation, last year as well. Meanwhile in Myanmar (Burma) a Tropical Storm drenched the western region and caused a massive landslide. More than 17,000 homes were destroyed, 46 people were killed, and hundreds of thousands of people were affected by the storm.



Southern Africa: A number of countries in southern Africa are reporting below average rainfall leading to drought conditions and fears of food insecurity. South Africa is in the midst of its worst drought since 1982, with 2.7 million households facing water shortages and farmers that cannot plant crops because of lack of precipitation. Some cities have implemented water restrictions, drastically reducing the amount of water residents can use. Regional prices for staple foods like maize meal, bread, eggs and chicken are up several percentage points. “When the maize crop goes down, the circumstances for social unrest go up … This is exactly how the Arab spring in the Middle East started,” said Louis Meintjes, president of the Transvaal Agriculture Union.



South America: Ecuador and Peru has suffered from flooding, extensive erosion, mudslides with loss of lives and infrastructure as well as damage to food supplies. Peru has declared a state of emergency as the country prepares itself for the worst weather system in over 60 years. Eastern Brazil is experiencing a major drought, driven by population pressure and deforestation, that could be worsened by dryer El Niño conditions. Satellite data shows the southeast of Brazil losing 56 trillion liters of water in each of the past three years - more than enough to fill Lake Tahoe. Water rationing, power blackouts and empty reservoirs in parts of the country have become a reality. More than 11,000 forest fires have been observed in the Amazonas province of Brazil this year, a 47% increase over the same period last year, according to the National Institute for Space Research. The storms that usually keep the jungles of southern Mexico and Central America wet shift northward to the southern US during strong El Niño winters. According to the World Food Program, 3.5 million people in Guatemala, Honduras and El Salvador need food aid due to drought and crop failures.




North America: According to NOAA, almost 95% of U.S. coral reefs will have been exposed to ocean conditions that can cause corals to bleach by the end of the year. El Niño has also contributed to a very active tropical cyclone season in the Western North Pacific and Eastern North Pacific. Hurricane Patricia, which made landfall in Mexico on 24 October, was reportedly the most intense tropical cyclone in the western hemisphere ever recorded. While category 5 Hurricane Patricia weakened rapidly after hitting the rugged terrain along Mexico’s Pacific coast, remnants of the storm combined with other weather systems over the Gulf of Mexico to produce heavy downpours and widespread flooding in Texas and Louisiana

El Niño conditions and disease risk

The development of these conditions also has important implications for global public health. Multiple epidemiological studies have linked El Niño events with increased incidence of disease outbreaks.




Disease
Region
Climatic influence
Cholera
Great Lakes region, Bangladesh, India (coastal), Sri Lanka, Peru
Warmer water temperatures promote bacteria proliferation; flooding causes contamination of water sources.
Dengue
Indonesia, Thailand, Pacific Islands, Australia (Queensland), Mexico, United States (southern), Colombia, Ecuador (coastal)
Water storage promotes mosquito vector breeding; elevated temperatures reduce the incubation period.Elevated rainfall promotes mosquito breeding.
Hantavirus
China (eastern), United States (southwest)
Elevated rainfall increases food availability for rodents which expands populations and may promote contact with humans.
Leishmaniasis
Brazil (eastern), Costa Rica, Colombia
Warmer temperatures or dry conditions may favor sand fly vectors or contribute to waning human immunity (e.g., via malnutrition or temporarily suppressing disease transmission).
Malaria
China (Anhui Province), India/Pakistan (Punjab), Sri Lanka, Colombia, Peru, Venezuela
Elevated rainfall promotes mosquito vector breeding and survival.
Plague
Madagascar, United States (western)
Heavy rains increase food availability for populations of susceptible rodents; cooler temperatures may increase infectious flea abundance.
Rift Valley Fever
East Africa
Flooding of dry mosquito vector habitats promotes hatching of infected eggs, vector breeding and survival.
Respiratory Illness
Southeast Asia/Indonesia
forest fires cause air pollution that may increase risk of respiratory infection

Ebola and Ecology

Emerging infectious diseases

Emerging infectious diseases (EID) may have a lot to do with changing environmental conditions and human-wildlife interaction. EID are either new types of pathogens or old ones that have mutated to become novel, as the flue does every year. Most known human EID are shared with animals meaning they are zoonotic. There is an excellent map over hot spots for EIDs in the world that was published in the New York Times back in 2012 that can be found here. While the research field, ecology-infectious diseases, is relatively new and crosses disciplinary boundaries I believe it should get more attention. Especially since it may tell us more about why EIDs have become so prevalent over the last couple of decades.


Ebola
While Ebola is a really scary disease because of its high fatality rate (50-90 %) its just one of nearly 1,000 known human diseases that have originated from animals. The specific source of the Ebola outbreak is not known, however, Ebola is thought to be naturally harboured in some species of bats. Initial transmission to humans may thus have come about via butchering or consuming bats or other infected species. VICE News made a great short documentary about bushmeat in the time of Ebola. While Ebola has had a devastating impact in west African countries it is unlikely that Ebola becomes a global pandemic since the infection pathway requires direct contact with bodily fluids. That said, the illegal bushmeat trade could potentially act as a transfer of the disease in to other countries around the world. Anyway, the Ebola outbreak serves as a reminder of the linkages between disrupted ecosystems and human illness.

Ecology
The more we humans expand our footprint and population, altering habitats and moving animals (and the pathogens they carry), the greater potential for infection and spread of pathogens novel to humans. For example, overfishing in an area could lead to an increase in bushmeat consumption due to subsistence standards which in turn could increase the prevalence of EIDs. Similarly deforestation forces animals to move into closer proximity to humans leading to closer contact, conflicts and loss of biological diversity. Moreover warming temperatures due to climate change may also change habitats and create new ones suitable for species and their pathogens. Examples range from mosquitoes to fruit bats.

Ebola Outbreak
Source: Future Earth
Coordination?
Some international groups such as WHO, Future Earth, Diversitas have come together and created the ecoHEALTH project, bringing together researchers from different fields to investigate connections between health and environmental change to generate policy outputs. Hopefully this crisis may shed some new light on prevention methods that include a better care for the worlds ecosystems and biodiversity. For example; combating illegal wildlife trade, improving sanitation, halting deforestation and securing more eco-friendly food production. At the moment many international help organizations are are instead struggling to keep up with all the emerging health crises. Doctors without borders (MSF) have their work cut out for them, combating both disease outbreaks and humanitarian crises, from outbreaks of MERS, Ebola and the Avian Flue to conflicts in South Sudan, Central African Republic and Syria. The organisations spokesperson begged the UN for more resources to combat the Ebola Outbreak, as many countries have not responded quickly enough to the crisis. One should understand that these are costly ways of trying to handling public health issues, much more can be done and to a lower cost on the side of prevention. We have the tools, now we only need foresight.

Conclusion
The complex dynamics of EID has become a hot topic. Hopefully more countries will start taking into account the overlapping drivers of disease and environmental change. Thinking of human health as separate from animal health and their determinants should be a thing of the past. Understanding the underlying parameters, such as human-wildlife proximity and habitat change, of disease outbreak could help organizations set up global monitoring services and look for early warnings of new outbreaks.